1. Field of the Invention
The invention pertains to equipment racks.
2. Art Background
A rack, as used in this disclosure, denotes a frame-like structure adapted to hold and display equipment, such as electronic equipment. Such racks are employed in a variety of settings including, for example, the central offices of telephone companies and hospital operating rooms.
In the past, the racks employed in, for example, telephone company central offices were used to hold the electromechanical relays employed in switching telephone calls between subscribers. Although switching is now typically achieved electronically, and the racks employed by the telephone companies are now more generally used to hold electronic equipment, including electronic telephone switching and electronic telephone transmission equipment, these racks are still often referred to as relay racks.
At present, the (relay) racks employed by the telephone companies are typically of two types. The first type, depicted in FIG. 1, is generally referred to as a channel relay rack, and conventionally includes generally parallel (in use, generally vertically oriented) steel frame members 10 and 20, which are U-shaped in cross section. The arms 11, 12, 21 and 22 (see FIG. 1) of these U-shaped frame members are apertured at regular intervals along their lengths, with the arms of one U-shaped frame member pointing toward the arms of the other U-shaped frame member. An angle iron 30 and an apparatus 60, which are welded or bolted to, respectively, the tops and bottoms of the U-shaped frame members, serve to connect the U-shaped members. In addition, the apparatus 60, often referred to as a guardrail, serves to prevent equipment mounted in the relay rack from being struck by the ladders used by operating personnel to inspect the equipment. That is, as shown in FIG. 1, the guardrail 60 includes two members 40 and 45 which, in cross section, have inverted L-shapes. The inverted L-shaped members 40 and 45 are connected to the bottoms, and extend between, the U-shaped frame members 10 and 20. A rectangular, sheet-like member 50, positioned between the U-shaped frame members 10 and 20, is connected to the inverted L-shaped members 40 and 45 via screws or bolts, and thus serves to connect the members 40 and 45 to each other. As is evident, the protruding flanges of the inverted L-shaped members 40 and 45 extend by a fixed distance from the front and back of the channel relay rack, and thus serve to deflect ladders from striking the equipment.
Significantly, the U-shaped frame members 10 and 20 are conventionally manufactured in four different heights, i.e., 7 feet (2.13 meters), 9 feet (2.74 meters), 101/2 feet (3.20 meters) and 111/2 feet (3.50 meters). As a consequence, the conventional channel relay rack is typically only available in four (corresponding) different heights.
Equipment is mounted in the conventional channel relay rack by initially attaching laterally projecting flanges to the front or back of the equipment. Then, the equipment is inserted between the frame members 10 and 20 until the laterally projecting flanges are flush with the arms of the frame members 10 and 20, and screws or bolts are inserted through apertures in the flanges aligned with apertures in the frame member arms. It must be noted that the equipment is mounted either before or after the rack is sold. That is, in many instances, equipment, such as the electronic equipment employed in telephonic signal switching or telephonic signal transmission, is mounted in the rack immediately after rack manufacture, and the equipment-filled rack is sold as an integral unit. Alternatively, the rack is sold empty of equipment, and equipment is mounted in the rack by the purchaser.
After a rack is sold (either with or without equipment) and installed, equipment mounted in the rack is typically examined and/or accessed with the aid of ladders. As discussed, the guardrail 60 serves to prevent the ladders from hitting the equipment.
In, for example, telephone company central offices, electrical power is delivered to equipment mounted in a channel relay rack through power cables extending from an overhead, generally horizontally positioned, ladder-like cable rack. Similarly, electrical signals are transmitted from, and received by, the equipment through transmission cables also extending from an overhead cable rack (different from that used for the power cables). In addition, in many instances, special purpose alarm cables are provided, extending from yet another overhead cable rack to the equipment, and from the equipment to remote alarm equipment in the telephone company central office, the alarm cables serving to communicate signals from the equipment to the remote alarm equipment indicative of equipment malfunctions. Significantly, further physical separation between the transmission cables and the power cables, beyond that achieved through the use of different cable racks, is needed to avoid creating spurious electrical signals in the transmission cables due to electrical noise in the power cables (the alarm cables are generally insensitive to such noise). This additional separation is achieved in a conventional channel relay rack, as shown in FIG. 1, through the use of right-angle steel brackets 70 and 80, generally referred to as cable brackets, bolted to the back of the relay rack. That is, in operation, the power and alarm cables are extended vertically downwardly from their respective overhead cable racks and positioned within, or immediately adjacent to, the corner formed by the arms of the cable bracket 70, from which they are further extended vertically and then horizontally into electrical contact with the mounted equipment. On the other hand, the transmission cables are also extended vertically downwardly from their overhead cable rack, but these cables are positioned within, or immediately adjacent to, the corner formed by the arms of the cable bracket 80, from which they are further extended vertically and then horizontally into electrical contact with the mounted equipment. As a result, the transmission cables are always spaced apart from the power cables.
While the conventional channel relay rack is useful, it does have several disadvantages. For example, the power, alarm and transmission cables are positioned outside of (rather than between) the arms of the U-shaped frame members 10 and 20, and thus these cables are exposed to inadvertent contact, and resulting damage, by operating personnel and passersby. In addition, it is often desirable to further separate the transmission cables according to function, i.e., according to whether the cables are used to transmit electrical signals to, or from, the mounted equipment, in order to avoid cross talk between the functionally different cables. However, this is not possible with a conventional channel relay rack because the cable brackets included in such racks serve to achieve nothing more than the physical separation of transmission cables (regardless of function) from power and alarm cables. Further, because the cable brackets 70 and 80 protrude from the relay rack, and are of steel, they represent a safety hazard to operating personnel. Additionally, because the conventional channel relay rack is entirely of steel, it is heavy and therefore difficult to install, whether or not filled with equipment, because much of the weight of a conventional, filled channel relay rack is attributable to the weight of the steel frame members. Moreover, because the conventional channel relay rack is not extendible (in terms of height), it is generally necessary to stock all four sizes of relay rack, which increases shipping costs and often necessitates the use of a relatively large amount of limited, and thus expensive, storage space.
The second type of relay rack employed by the telephone companies is depicted in FIG. 2 and is generally referred to as a duct-type relay rack. As shown in FIG. 2, a conventional duct-type relay rack is similar to a conventional channel relay rack in that it includes two generally parallel (in use, generally vertically oriented) steel frame members 110 and 120 which are U-shaped in cross section and have arms which are apertured. However, by contrast with the conventional channel relay rack, the arms 111 and 112 of the frame member 110 point away from the arms 121 and 122 of the frame member 120. In addition, the arms 112 and 122 have identical widths which are smaller than the identical widths of the arms 111 and 121. In all other respects, the conventional duct-type relay rack is generally structurally similar to the conventional channel relay rack. That is, the conventional duct-type relay rack further includes steel cross members 130 and 140 connected to, respectively, the tops and bottoms of the U-shaped frame members 110 and 120, as well as a steel guardrail 160 (of the type pictured in FIG. 2) projecting (by a fixed distance) from the bottom of the duct-type relay rack.
In use, the conventional duct-type relay racks are often placed very close to one another, and thus the relatively wide arms 111 and 121 (see FIG. 2) of the U-shaped frame members of one relay rack often project into contact, or into close proximity, with the corresponding arms of the U-shaped frame members of adjacent duct-type relay racks. Moreover, any intervening space between the adjacent, relatively wide arms is often covered, at least in part, by a plate. As a consequence, two substantially enclosed, vertical ducts (hence the name of the relay rack) are formed on the opposite sides of each duct-type relay rack. In addition, the smaller widths of the frame member arms 112 and 122 (see FIG. 2) results in a gap between the arm 112 of one rack and the arm 122 of an adjoining rack, thus permitting access to the rear of the vertical duct formed by the arms of the two racks. Significantly, in use, the power and alarm cables are extended vertically downwardly into one such (substantially enclosed) vertical duct, the transmission cables are extended vertically downwardly into the other such vertical duct, and both sets of cables are then extended horizontally (out through the gaps in the vertical ducts) into electrical contact with the mounted equipment. Thus, this rack configuration is advantageous because, while the power and transmission cables are physically separated, all the cables are largely enclosed by the arms of adjacent U-shaped frame members, and therefore protected against inadvertent damage by operating personnel.
Although the conventional duct-type relay rack has a configuration which prevents inadvertent damage to power, alarm and transmission cables by operating personnel, it, like the conventional channel relay rack, is incapable of achieving physical separation between functionally different transmission cables, i.e., between the transmission cables used to transmit, and receive, electrical signals. The conventional duct-type relay rack is also entirely of steel, and thus heavy and difficult to install. In addition, like the conventional channel relay rack, the duct-type relay rack is not extendible (in terms of height), i.e., it is only manufactured in the four different sizes, given above. Because all four sizes must generally be stocked, the use of the conventional duct-type relay rack also involves high shipping costs and also requires the use of a relatively large amount of limited, and therefore expensive, storage space.
Thus, those engaged in the development of equipment racks have sought rack configurations which achieve physical separation between different types of cables, such as power and transmission cables, as well as between functionally different cables of the same type, such as transmission cables used for transmitting, and receiving, electrical signals, without the use of hazardous (to operating personnel) cable brackets. In addition, and equally importantly, those engaged in the development of equipment racks have also sought rack configurations which prevent inadvertent damage to cables, are height extendible, and are relatively light and therefore relatively easy to install.